Relay Backhaul Reference Signal Mapping for Missing OFDM Symbols
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Solution Overview
Problem
In wireless communication relay systems, efficient transmission of signals and reference signals is hindered when relays fail to receive the last Orthogonal Frequency Division Multiplexing (OFDM) symbol of a subframe, leading to resource wastage and poor channel estimation.
Innovation Solution
The method involves mapping a Reference Signal (RS) to a subframe with two slots, where the RS is spread across consecutive resource elements overlapping with the last OFDM symbol. If the last OFDM symbol is not available, the RS is transmitted only in the first slot, and data is mapped to the second slot using orthogonal codes, optimizing resource utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the Reference Signal is spread across consecutive resource elements overlapping with the last OFDM symbol, then channel estimation accuracy is improved, but resource overhead increases when the last OFDM symbol is not received by the relay
Solution Approach 1:
The patent applies local quality by differentiating the treatment of resource elements based on their position and availability. Resource elements in the first slot are always used for RS transmission, while resource elements in the second slot are conditionally used - only if the last OFDM symbol is successfully received. This localized differentiation optimizes resource utilization by avoiding overhead in unavailable regions while maintaining estimation accuracy in available regions.
Solution Approach 2:
The patent changes the transmission parameter of the Reference Signal based on reception availability. When the last OFDM symbol is not received, the system transitions from transmitting RS across both slots to transmitting RS only in the first slot. This parameter change adapts the resource allocation to the actual reception conditions, reducing overhead while maintaining channel estimation capability.
2Loss of substance
If the Reference Signal is transmitted only in the first slot when the last OFDM symbol is not available, then resource overhead is reduced, but channel estimation accuracy deteriorates
Solution Approach 1:
The patent applies partial action by transmitting the Reference Signal in only one slot (the first slot) when the last OFDM symbol is not available, rather than transmitting in both slots. This partial transmission reduces resource overhead while still providing sufficient channel estimation capability for the available data, accepting a trade-off in estimation precision to achieve resource efficiency.
3Productivity
If data signal is mapped to resource elements in the second slot using orthogonal codes, then resource utilization is improved, but signal interference increases
Solution Approach 1:
The patent uses orthogonal codes as an intermediary mechanism to separate the data signal from potential interference. By mapping the data signal to resource elements in the second slot with orthogonal codes, the system enables resource utilization while the orthogonal properties of the codes provide isolation from interference, allowing simultaneous transmission without excessive harmful interactions.
Data Source
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AI summary
A method and apparatus for transmitting a signal to a relay at a Base Station (BS) in a wireless communication system are disclosed. The method includes mapping a Reference Signal (RS) to a subframe having two slots, and transmitting the subframe to the relay. Each of the slots includes a plurality of consecutive resource elements over which the RS can be spread and the plurality of consecutive resource elements are overlapped with a last Orthogonal Frequency Division Multiplexing (OFDM) symbol of the slot. If a last OFDM symbol of the subframe is not available to the relay, the RS is transmitted only in a first slot of the subframe.